Average error rate analysis for pilot-aided OFDM receivers with frequency-domain interpolation

In OFDM receivers, pilot tones should be inserted among the sub-carriers in order to estimate the channel in high delay spread environments. To estimate the channel at all the sub-carriers, using the pilot tones, different frequency-domain interpolators can be used. For a given number of pilot tones, these interpolators will have different levels of complexity depending on the number of adjacent pilot tones that they use to estimate the channel at each sub-carrier. For high delay-spread channels, as the number of adjacent pilot tones used by an interpolator increases, channel estimation improves resulting in a tradeoff between performance and complexity. In this paper, we first find an analytical average error rate formula for a pilot-aided OFDM receiver in a delay spread fading environment. This analysis will provide a framework to evaluate the performance of different interpolators. As an example, we then evaluate and compare the performance of two interpolators with different levels of complexity: a trigonometric interpolator and a linear one. We derive the average error rate formulas of the interpolators and confirm that the former one has a considerably better performance as the delay spread increases. However, for flat fading channels, we show that the linear interpolator has a 3 dB gain. Finally, our simulation results support the mathematical analysis and comparison.